Radio frequency identification (RFID) systems are capable of wirelessly detecting individual RFID tags (herein referred to as “tags”) as they pass in the vicinity of an RFID reader. Unlike bar codes, which are read individually and must be in the optical line-of-sight of the scanner, RFID tags can rapidly read a large number of tags that are within a region around a reader, such as a number of tagged products that are together on a shelf or a pallet. Moreover, tags may be read through some materials, such as paper or plastic packaging material used to ship cases or pallets of products. As such, individual products may be tagged and read after being placed in a container for storage or shipment.
RFID tags may be wafer-thin, microchip-based tags about the size of a large postage stamp. The tags may include antenna features capable of receiving radio frequency energy to communicate with a reader. Typically, a reader may detect a tag by transmitting radio frequency (RF) energy at a particular frequency and with a particular modulation. A tag within the appropriate range of the reader may be energized by the RF energy received via the tag's antenna. The energized tag may respond by generating or reflecting an RF signal that may be detected by the reader's antenna and receiver. The signal sent by the tag may be encoded with information, such as a serial number, electronic product code (EPC), stock keeping unit (SKU), or other identifying information. After the reader receives and decodes the identifying information, the presence of the tag may be recorded or stored for various uses. When individual tags are associated with products in a distribution chain, for example, uses may include, but are not limited to, inventory management, product tracking, billing, loss prevention, or ordering.
Product tracking in a distribution chain may use RFID systems to track inventory, for example, at various control points in a manufacturing plant, distribution centers, warehouses, and retail outlets. In a practical large scale RFID system, not all tags may be read. In the distribution chain context, RFID system performance may generally refer to the reliability with which tags are read as products move through the distribution chain.
At each of these points, the margin by which tags are satisfactorily read is subject to various parameters, such as temperature and humidity conditions, electromagnetic interference (EMI), reader/tag sensitivity, material properties, and numerous other factors that can impact how reliably tags are detected by the RFID system. Accordingly, reliably tracking tags in such environments requires the RFID system to operate under various atmospheric, electromagnetic, and other conditions that can impact RFID system performance.